1. Technical Field
Apparatuses and methods consistent with the present inventive concept relate to rotating media, and more particularly to controlling current in a voice coil motor drive circuit.
2. Related Art
Conventional Voice Coil Motor (VCM) control systems used in hard disk drives (HDDs) use resistors disposed externally to control integrated circuits for measuring VCM drive current and providing feedback to a current control loop. FIG. 1 is a diagram illustrating a conventional control circuit 100 for a voice coil motor. As illustrated in FIG. 1, the VCM 120 is electrically coupled to an H-bridge circuit 110 at a first connection terminal 112 and a second connection terminal 114. Current to operate the VCM 120 is provided by the H-bridge circuit 110 through a third connection terminal 116, a resistor 130 and the second connection terminal 114. The drive current supplied by the H-bridge circuit 110 is controlled based on an error signal 182 generated by an error amplifier 180. The error amplifier 180 generates the error signal 182 based on an input signal from a first sense amplifier 140 and an input signal from a feedback controller 170.
The drive current through the VCM 120 is measured as a voltage drop created across the resistor 130 from the third connection terminal 116 to the first connection terminal 112. The differential voltage across the resistor 130 is sensed by the first sense amplifier 140 that provides an input signal to the error amplifier 180 and by a second sense amplifier 150 that provides an input signal to a feedback amplifier 160. The feedback amplifier 160 provides a feedback signal 162 that closes the gain loop with the feedback controller 170. In FIG. 1, the VCM 120, resistor 130, and the first, second, and third connection terminals 112,114, 116 are external to the control circuit 100.